1. Field of the Invention
The present invention relates to laser processing machines which can process sheet-like workpieces such as sheet metals by various methods such as cutting and piercing by use of laser beams produced by laser resonators.
2. Description of the Prior Art
As is well-known, laser beams are widely used in industries to process a variety of metallic and nonmetallic materials such as irons, nickels, plastics, rubbers and glasses. In laser processing, the laser beams are produced by a laser resonator and are applied together with an assisting gas such as oxygen gas (O.sub.2) to a material to be processed through a nozzle after being focussed by a condenser lens.
Heretofore, however, the laser beams have been little used to process sheet-like workpieces such as sheet metals in large quantities by cutting and piercing, and there have been no machines specially designed to process sheet-like workpieces. As a matter of importance, in order to perform an accurate and fine processing by use of the laser beams, it is necessary to focus the laser beam by the condenser lens to a minimal diameter on the workpieces to be processed. For this purpose, it has been desired to accurately adjust the focal position of the condenser lens according to sizes or thicknesses of the workpieces to be processed. Also, since sheet-like workpieces such as sheet metals are more or less bent or warped, it is desired to feed such sheet-like workpieces so that portions thereof to be processed may be located at the focussed point of the laser beam, namely, the focal point of the condenser lens. Therefore, it is also desired to resiliently change the focal position of the condenser lens during processing according to the bends or warps of the sheet-like workpieces. Furthermore, it has been desired to easily change the condenser lens for focussing the laser beams since the condenser lens is liable to be deteriorated.